Chloridizing roasting of ores.



A. RAMEN & K. J. BESKOW. GHLORIDIZING ROASTING 0F ORBS. APPLICATIONFILED AUG. 1a,191o..

Z SHEBTSSHEET 1- )NVENTORS wnrmzssas Patented Feb. 23, 1915.

A. RAMEN & K. J. BESKOW. GHLORIDIZING ROASTING 0F ORES APPLICATION FILEDAUG. 18, 1910.

1 9 1 9, 1 3 Patented Feb. 23, 1915.

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GHLORIDIZING- ROASTING- 0F ORES.

Specification of Letters Patent.

Patented Feb. 23, 1915.

Application filed August 18, 1910. Serial No. 577,844.

To all whom it may concern:

Be it known that we, ARTHUR RAMriN and KNUT JAKoB BESKOW, chiefengineers, subjects of the King of Sweden, residing in Siidra Storgatan19, Helsingborg, in the Kingdom of Sweden, have invented certain new anduseful Improvements in and Relating to the Chloridizing Roasting ofOres, of which the following is a specification.

Roasting ores for the purpose of converting them into chlorids hashitherto been per formed either by bringing a mixture of ore andchlorids into direct contact with the smoke or combustion gases infurnaces, or by heating the mixture in muflles, where the smoke gasescommunicate to the ores the heat necessary for the process indirectly i.0. through the walls of the muffles. first case there is thedisadvantage that the acid gases, generated during the chloridizingprocess, become diluted or befouled with such large quantities of thecombustion gases used for the heating of the material, that it is notpossible to fully extract the acids contained in the said mixture ofgases, besides which the acid obtained is considerably inipure anddiluted. This disadvantage is avoided in the latter case by the use ofmul'lle furnaces, but then there is the drawback that the consumption offuel is very much increased on account of the inferior heatingefficiency of the muflies. Attempts have also been made to employmechanical furnaces for carrying out this process, and among otherthings it has been proposed first to heat the ore mixed with salt directwith combustion gases in a furnace or section of a furnace, and thencause the ore to descend to another furnace or compartment of a furnaceprovided with a muflle, in which furnace or compartment the chloridizingtakes place with the contribution of heat from the muffle walls. Thesmoky gases are conducted according to this method first through themuffle compartment and afterward direct into the first compartment, 2'.e. the heating compartment. Arrangements are made to enable the materialto descend into the latter compartment, 2'. c. the chloridizingcompartment, without the acid gases which are developcd in thechloridizing compartment being mixed with the smoky gases in the heating compartment. In this method there is, no doubt, the advantage thatthe gases can be obtained unmixed from the chloridizing In thecompartment, and moreover a better heateconomizing effect has beenobtained than if merely a mu'iile furnace were employed, as part of theheat is supplied by direct con tact with the smoky gases. In employing,however, the supply of heat by means of a mutlle encounters inmechanical chloridizing furnaces considerable difiiculties. For, inorder that the chloridizing process may take place the roasted mattermust have a temperature of 4()0600 G, and consequently the mufile wallsmust have a temperature of 700800 C. At this temperature, however, themixture of the salt and the ore partially melts, and in consequence themuffle bottom gets caked over. As a consequence of this, the temperaturein the mufiie must be additionally increased, the consequence of wh1chagain is that a still thicker layer forms on the bottom. As a matter offact, repeated attempts to employ muffle furnaces for chloridizingroasting have broken down owing to mechanical difficulties. In theemployment of a muflie there is also the difliculty that over-heating ofthe material ensues, which causes losses of metal partly owing to thefact that a part of volatile metallic chlorids evaporate and are carriedoff with the acid gases, or, thatsome basic metallic chlorids are formedwhich in the leaching out process which is afterward to be carried outwith the materials do not readily admit of being leached out with waterand weak acids. Even if over-heating does not as readily take place in afurnace with mechanical stirring, as in a hand muflle furnace,nevertheless the drawback is so great that it is a factor to be reckonedwith.

In contradistinction from the method referred to above, We do not employany additional heating of material in the chloridizing compartmentsupplied from without, by means of a muffle, but, instead, we introducethe smoky gases direct from the source of heat into the heatingcompartment. In this way we are able to bring about a higher degree ofheating in the heating compartment, 2'. 6. right up to a temperaturewhich is only a trifle lower than that at which chloridizing commencesand at which acid gases are introduced. The material, heated in this wayto a suitable temperature is brought from the heating furnace (orcorresponding compartment or zone of a furnace comprising both a heatingfurnace and a chloridizing furnace) into the chloridiging furnaceor-into the corresponding compartment or zone of the said combinedheating and chloridizing furnace (said chloridizing furnace orchloridizing compartment or zone being also in the following designatedonly as chloridizing furnace) before the acid gases have been developedto any degree worth consideration. Then the chloridizing process underinfluence of the heat thus applied and the heat developed by thechloridizing process itself takes place in this latter furnace undercontinuous mechanical stirring of the material and admission of airwithout it being necessary to supply heat from without. The acid gasesdeveloped during the process are led off as before known from thechloridizing furnace separated from the combustion gases led intotheheating furnace for heating the material to be treated. By a suitablecomposition of the mixture of the ore and chlorids and heating of thematerial in the heating furnace to a suitable temperature, the heat thusgiven to the material together with the heat devel-' oped in thechloridizing furnace by the reaction between the sulfurous metals contained in the ore, the chlorids and the air supplied for the oxidationis suflicient' to raise the temperature of all the mixture treated tothe temperature at which the chloridizing roasting will begin andcontinue, z. e. it will not be necessary to supply any combustion gasesor any more heat to the ore mixture during the chloridizing processitself. The material usually treated in this way is worked for copperand contains for instance 2- 1 per cent. copper and 3-6 per cent. sulfurand for treating the same according to our invention at first there isadded chlorid in suflicient quantities, for instance 10-12. per' cent.common salt. The mixture of the materials to be roasted and the commonsalt ground and intimately mixed is then heated in the heating furnaceor compartment to about 300 degrees centigrade by direct contact withcombustion gases and thereafter said mix-.

ture is brought down into the chloridizing furnace or compartment where,owing to the effective mechanical stirring, the temperature is raised to500-600 degrees centigrade only on account of the heat of reaction ofthe material and the heat supplied in the heating furnace. Thus it isunnecessary to supply any additional heat to the chloridizing furnace orcompartment. It is evident that this method may be carried into effectin many diflerent ways. .Thus the whole mixture of oreand chlorid can beheated in the heating zone or the heating furnace to a temperaturesuitable for the reaction, and then allowed to drop down to thechloridizing zone of the same furnace or may be transported into anotherfurnace serving as the chloridizing furnace, or only.

a part of the ore may be heated alone, without adding chlorid, and canafterward be .brought together with a mixture of the remaining part ofthe ore and chlorid simultaneously with, or after this mixture beingbrought into the chloridizing compartment or zone of the combinedfurnace or into the chloridizing furnace. As, in some cases, it is notnecessary for obtaining a temperature suitable for carrying on thereaction to heat 7 the whole mixture of ore the advantage will be gainedby performingthe process according to the modification last describedthat a smaller apparatus can be used, and that the loss of heat issmaller and therefore the efiiciency greater. It is also possible toheat all the ore to a suitable temperature in the heating furnace (orthe heating compartment) and then add chlorid to this heated ore, whichis then transported to the chloridizing furnace or chloridizingcompartment, where the reaction takes place without it being necessaryto supply heat through the muflle. In some cases this latter method ismore advantageous or must under certain circumstances be used, while,when heating ores which contain too small a quantity of sulfur theamount of heat necessary cannot suitably be supplied to the material inthe heating furnace in the case that the ready mixture of ore andchlorid should be charged into said furnace. If the mixture of chloridand ore of said kind should be heated in the heating furnace to such ahigh temperature, which is required for the treating of saidores,which,by the reaction, do not themselves give ofi' a sufficientamount of heat of reactionthat it should not be necessary to supplyfurther heat in the chloridizing furnace from the outside of the same,reaction between the chlorid and the ore would take place already in theheating furnace and thus acid gases would be lost together with thesmoke gases introduced into said furnace for the heating. Ifinstead theore alone, which sustains a considerable high temperature, is heated inthe heating furnace, a sufiicient quantity of heat may in that furnacebe supplied to the ore without any loss of acid gases, and then, 5 afteradmixture of chlorid, or a mixture of chlorid and ore, the reaction maybe introduced and finished in the chloridizing furnace, without it beingnecessary to supply further heat to the material in thislatter furnace.

By means of this invention it is possible while obtaining pure andconcentrated gases, to obtain a small consumption of coal, as allheating of the material takes place by direct contact with smoky gases.By not employing a mufile,all the mechanical difficulties whichotherwise ensue owing to the caking of the material on the mufilebottoms, are obviated. Owing to the fact that while the-chloridizingprocess itself is go ing on, the material -is not brought into contactwith heated gases or heated wall-surfaces, muflles, over-heating of thematerial and the above described loss of metal thereby caused, isobviated.

For carrying out the processlof'chloridizing described herein, a numberof different types of furnaces may be used varying with the nature ofthe ore.

As already mentioned the heating and the chloridizing can take place inseparate furnaces. For this purpose such furnaces may be used whichconsist of rotating cylinders or immovable furnaces'having rotating orreciprocating stirring devices or some other known type of mechanicalroasting furnace.

lit is of course'also possible to perform the whole process in one-andthe same furnace, the heating compartment and the chlofidizingcompartment being separate from each other as known before, or by meansof automatical registers, partitions or other suitable devices, in whichcase the heated material can be brought down from the heatingcompartment into the chloridizing compartment in a suitable manner (forinstance by means of feeding pistons or feeding screws), so that noquantity of gas Worth consideration can pass from one division into theother. Characteristic of the invention is that the latterfurnace orcompartmentis not provided with a muflie and that the smoky orcombustion gases are introduced from the source of heat directly intothe heating compartment.

In the accompanying drawings a suitable furnace for carrying out theprocess is shown in Figure 1 'in' vertical section and Fig. 2 shows insection a part of the same furnace provided with an extra feeding devicefor introducing material directly into the chloridizing compartment.

1 is the brickwork of the furnace suitably surrounded by a mantle 6 ofmetal and provided with arches 2 and 3 forming'the top and the bottom ofthe same and also provided with intermediate archesor bottoms,

4 and 5 (of any suitable number) by means of which the furnace isdivided into several divisions or compartments.

7 is a feeding funnel supported byshores 68 resting on beams 8 supportedon the The feeding table 11 is mounted on the upper end of a centrallylocated vertical, rotating shaft 12 -journaled in bearings 13 and 14;.The lower or main part of said shaft may consist of a tube, provided"with openings 39 for admitting air to enter into the same for itscooling. 1 v

15 are scrapers extending some distance over the periphery of thefeeding table 11, and consisting of arms, which at their outer ends areadjustably fastened on standards 16 in such a .way, that they by meansof screws 17 can be secured in any desired position in order that theinner ends of said arms; or scrapers proper may be brought to protrudemore or less over the outer edge of the table. Thus, when the table isrotated and material is fed into the funnel 7 a desired quantity of thematerial (depending on the position of the scrapers): is by saidscrapers continuously fed from the rotating table into the channels ortubes 18, that are arranged under the circumference of the table, andthrough I which tubes the material falls down into the upper compartmentor division19 of the furnace. These channels or tubes may be providedwith self closing shutters 42, pivotally fastened on bolts 41 and loadedwith counterweights 7 3, which shutters open automatically when acertain quantity of the material, fed into the tubes, has beenaccumulated upon them but are otherwise closed, through the action ofthe counterweights, thereby preventing gases from the furnace rising upthrough them.

In. the arch 5' which separates the heating compartment 19 of thefurnace from the chloridizing' compartment formed by the di visions 20,'21 one or several channel or channels 22 are arranged through which thematerial heated may pass from the heating compartment down into thechloridiz ing compartment. In the arch .4 there is also a centralopening or channel 23, through which the material can fall down from thedivision 20 into the division 21, from which latter division thematerial treated is carried off through a channel (or several channels)24 in the brickwork, said channel'24 being normally closed by a selfclosing shutter 25, pivotally hinged on a bolt 26 and provided with acounterweight 27 so arranged, that the shutter by the action of the sameis normally closed but opens automatically when a certain quantity ofthe material has been accumulated in the channel 2 1 and presses againstthe shutter.

For stirring and transporting the material through the furnace the'following devices are provided: Within each of the several divisions 19,20, 21 one or several arms 28 removably attached to the rotating shaft12 extend radially from said shaft. Said arms are provided with scrapers29 or similar devices extending down into the material resting on thebottoms of the corresponding divisions and stirring the same as the arms28 rotate with the shaft 12. In order that the material may betransported across the furnace to the outlet channels 22, 23, 24 of theseveral divisions, said scrapers may consist of blades, which form anoblique angle to the length direction of the arms supporting the same sothat when the shaft rotates, the material in the division 19 istransported from the center to the periphery, where it falls downthrough the channel 22 into the division 20, in which division thescrapers are so arranged that the material is transported from theperiphery to the center, where it falls down through the channel 23 intothe-division 21,

in which division the material is again transported in the same way as"in division 19 to the periphery, where it is carried off from thefurnace through the channel 24.

For rotating the shaft 12 any suitable device may be used. In thedrawing this device is shown as consisting of belt disks 30, mounted onthe one end of a rotating shaft .31, which on its other end is providedwith a bevel-wheel 32 which gears with a bevel wheel 33 mounted on thelower end of the izing compartment from rising through the channel 22into the heating compartment, where it otherwise would be mixed withsmoke gases and thus freed together with saidgases, the followingarrangement is provided: In the channel 22 is inserted a funnel shapedtube or sleeve in which 18 arranged a shutter 60, pivotally hinged onbolts 61 and by means of a projection 66 and a link 62 connected withone end 65 of an angular lever, pivotally hinged on a support 64projecting from the furnace wall, the other end of said lever beingprovided with a counterweight, so that the shutter by the action, ofsaid counterweight is normally held in closed position but opens as soonas a sufficient quantity of material from the heating compartment hasbeen accumulated upon the .same, whereby it discharges said material inthe lower funnel shaped part of the sleeve. -As the lower mouth of saidsleeve is constricted, the ma terial does not at once pass through thesame but is stopped there and forms a gastight seal at least until theshutter has again had time enough to close itself. By this devicegasesare prevented from passing between the two compartments although thematerial to be treated passes from the one compartment into the other.This sealing device may however be substituted for any other devicesuitable for the purpose.

In order to prevent gases from escaping from the furnace around theshaft 28 vat the bottom and the top .of the furnacesa'nd-sealings ofknown construction are provided at those places, consisting of anannular groove or cup 36 fastened to the brickwork and filled with sandor the like and a collar 37 fastened to the shaft the lower edges ofwhich collar enter into the sand in the corresponding groove 36, thusforming a gas tight seal. 38 are openings in the wall closed byremovable shutters 39, through which openingsaccess to the interior ofthe furnace is provided for carrying out any work or repairing that isrequired. 40 is an opening for admitting air into the chloridizingdepartment. The area of said open-. ing may be regulated by means of anadjustable damper 41 in order to control the supply of air. 42 is anoutlet for the chlorin gases developed in the chloridizing department.43 is an inlet for generator gases (or other gases) used for heating thematerial in the heating department and 44 is a pipe through which theair necessary for combustion of said gases is introduced.

45 is an outlet'for the gases, used for heating the material. Thisfurnace (which is shown only as an example) works in the followingmanner: The material to be treated consisting of a mixture ofore, forinstance roasted (oxidized) pyrites, and chlorids, for instance commonsalt, is charged into the funnel 7 and from thence it is by means of therotating feeding table 11 and the scrapers 15 fed in a continuousstream, as above described, down into the heating compartment 19 throughthe tubes 18. Generator gas is also introduced into said heatingcompartment through the pipe 43, and is there burned by air introducedthrough the pipe 44, whereby the material is heated to any desiredtemperature (which temperature can be regulated by regulating the supplyof said gases). At the same time the material is continuously stirred bymeans of the scrapers 29 and transported to the channel 'a furtheramount of chlorid or ore or a m1xture of chlorid and ore may also bedirectly supplied to the chloridizing compartment as above stated forinstance by means of a feeding screw or the like as shown in Fig. 2. Inthis figure 78 is a funnel or hopper communicating with the one end of afeeding pipe 79, the other end of which communicates with thechloridizing compartment 20 of the only of one stage or division, whilethe ch10 ridizing compartment comprises two stages or divisions. It ishowever to be understood that each compartment may comprise any suitablenumber of stages or divisions communicating with each other in themanner above elucidated.

In the process above described a complete separation of the acid gasesgenerated in the chloridizing compartment and the gases used for heatingthe material in the heating compartment takes place, which separation isefi'ected by the use of such 'a seal or tightening device between thesaid compartments,

that material to be treated may pass from the heating compartment intothe chloridizing compartment while at the same time gases are preventedfrom passing from the one compartment into the other. When,

however, such materials are to be treated,

which, when mixed'with chlorids, easily become cloddy it may happen,that said devices do not act satisfactorily, but instead the passagebetween the two compartments gets stopped. In order to get rid of thesedisadvantages the said sealing devices may be left out which can be donewithout any considerable mixing of the gases from the heatingcompartment and the chloridizing compartment is caused if the process isthus carried out that the gases in the heating compartment are given asomewhat higher pressure than the gases in the chloridizing compartment.By this manner of working the valuable acid gases developed in thechloridizing compartment are fully prevented from entering into theheating compartment and the main part of the com- 'bustion gases in thislatter compartment can easily be led off for instance to the chimney,while the gases-in the chloridizing compartment are led to a condenser.No gastight sealing being provided in the channel through which theheating compartment and the chloridizing compartment communicate witheach other, obviously, on account of the higher pressure in the heatingcompartment some combustion gases'will enter from that compartment intothe chloridizing compartment, but, if the difference in pressure of thegases in the two compartments is suitably regulated the quantity ofcombustion gases, which enter into the chloridizing compartment is sosmall that no disadvantageous dilution or vitiation worth mentioning ofthe gases in the last named compartment is caused. For the rest, in somecases it may be advantageous to supply some heat to the material in thechlo ridizing compartment, for which purpose it is well to introducesome combustion gases into said compartment. 'Ihe principal object is,however, that all or at least the main part of the combustion gaseswhich in the heating compartment directly act on the material to betreated may be directly led oil from that compartment without causingany loss of the acid gases in the chloridizing compartment.

For carrying out this modified form of the process in question, amongother furnaces, a usual roasting furnace of the so called Mac Dougallstype may be used, 71. e. a standing cylindrical furnace with a centralvertical shaft and several annular bottoms arranged one above the other,on which bottoms the ore is transported from the one bottom to the otherby means of stirring devices extending from and connected with thevertical shaft. If a furnace is used provided with for instance fivebottoms, the heating gases or smoke gases used for the heating of thematerial may be introduced in the space between the first and secondbottom from the top and led off from the space or division formed abovethe first bottom from the top. These two spaces or divisions in thiscase form together the heating zone. The gases generated by thechloridizing process may in this case be carried off from the divsionformed under the second or third bottom from the top. Thus in this casethe chloridizing compartment is formed by the three lower divisions ofthe furnace. The said difierence in pressure can for instance beobtained by having the two compartments work under difierent vacuum(draft) or by having the heating compartment work under overpressure andthe chloridizing compartment work under vacuum (draft) orfinally in sucha way that overpressure is present in both compartments, but is higherin the heating compartment. The expression overpressure as above used,refers to the atmospheric pressure.

In all cases the gases in the heating compartment are kept at a somewhathigher absolute pressure than the gases in the chloridizing compartment.In case overpressure iskept in the heating compartment this overpressuremay be caused by having the air necessary for the combustion introducedun-- pressure is used also the chloridizing compartment and the gasesare to be led off from that compartment under pressure, the airnecessary for the chloridizing process which air causes the formation ofthe acid gases ((3,, S and S0 is introduced under overpressure in thesaid compartment.

In the following claims the words furnace member are used for thedesignation of a separate furnace as well as a special compartment orzone of a furnace comprising 0th a heating compartment and achloridizing compartment.

Having thus described our invention, we

declare, that what we claim is 1. The herein described process forchloridizing roasting of ore and the like, which consists of heating thematerial to be treated in a furnace member by direct action of hot gasesintroduced into said furnace member, subjecting the heated material tothe action of a chloridizing agent in a second furnace member, andallowing the chloridizing.process to take place in the second furnacemember under continuous mechanical stirring and under the influence ofthe previously applied heat and the heat developed by the 'member, andallowing the chloridizing process to takeplace in the second furnacemember under continuous mechanical stirring and under the influence ofthe previously applied heat and the heat developed by the -chloridizingprocess itself, without additional supply of heat from an externalsource, and drawing off the gases developed in the last-mentionedfurnace member during the chloridizing process separate from the heatinggases introduced into the firstnamed furnace member, the gases in thefirst named furnace member being kept at a higher pressure than thegases in the other furnace member.

3. The herein described process for chloridizing roasting of ore and thelike, which *consists in heating a mixture of the material to be treatedand the'chloridizing agent in a furnace member by direct action of hotgases introduced into said furnace member, transferring the heatedmixture to a second furnace member and allowing the chloridizing processto take place in the second furnace member under continuous mechanicalstirring and under the influence of the previously applied heat' and theheat developed by the chloridizing process .itself, without additionalsupply of heat from an external source, and drawing off the gasesdeveloped in the last-mentioned furnace member during the chloridizingprocess separate from the heating gases introduced into the firstnamedfurnace member.

4. The herein described process for chloridizing roasting of ore and thelike, which consists in heating a mixture of the material to'be treatedand the chloridizing agent in a furnace member by direct actlon of hotgases introduced into said furnace member, transferring the heatedmixture to a second furnace member, adding a quantity of one of theingredients thereof and allowing the chloridizing process to take placein the second furnace member under continuous mechanical stirring andunder the influence of the previously applied heat and the heatdeveloped by the chloridizing process itself, without additional supplyof heat from an external source, and drawing off the gases developed inthe last mentioned furnace member during the chloridizing processseparate from the heating gases introduced into the first-named furnacemember.

' 5. The herein described process for chloridizing roasting of ore andthe like, which consists in heating a mixture of the material to betreated and the chloridizing agent in a furnace member by direct actionof hot gases introduced into said furnace member, transferring theheated mixture to a second furnace member, adding a quantity of thechloridizing agent, and allowing the chloridizing process to take placein the second furnace member under continuous mechanical stirring andunder the influence of the previously applied heat and the heatdeveloped by the chloridizing process itself, without additional supplyof heat from an external source, and drawing off the gases developed inthe last mentioned furnace member during the chloridizing processseparate from the heating gases introduced into the first-named furnacememben- 6. The herein described process for chloridizing roasting of oreand the-like, which consists of heating the material to be treated in afurnace member by direct action of hot gases introduced into saidfurnaie member,

transferring the heated material 0 a second furnace member, adding achloridizing agent and allowing the chloridizing process to take placein the second-furnace member under continuous mechanical stirring andunder the influence of the previously applied heat and the heatdeveloped by the chloridizing process itself, without additional supplyof heat from an external source, and drawing off the gases developed inthe last mentioned furnace member during the chloridizing processseparate from the heating gases introduced into the first-named furnacemember.

7. In the chloridizing of ores by heating such ores by fire heat in onechamber and by finishing and chloridizing in another and adjacentcommunicating chamber the process which comprises maintaining said firstfire-heated chamber under greater, pressure than the secondcommunicating chloridizing 10 chamber.

In witness whereof we have hereunto set our hands in presence of twoWitnesses.

ARTHUR RAMEN. KNUT JAKOB BESKOW. Vitnesses EWA VON EssEN, M. KJcUs'moUs.

